Mount Pleasant Water Hardness & Quality Report (2026)

Mount Pleasant, South Carolina — the largest municipality in Charleston County, on the east bank of Charleston Harbor across from the historic Charleston peninsula — draws its municipal water supply through Mount Pleasant Waterworks (MPW), sourcing from the Bushy Park Reservoir (an impoundment on the Cooper River in Berkeley County) and the Edisto River wellfield via the regional Commissioners of Public Works (CPW) infrastructure. The Bushy Park Reservoir is the primary water supply source for the Charleston area. Water hardness in Mount Pleasant measures 96 mg/L — classified as moderately soft.

Mount Pleasant's moderately soft supply reflects the coastal South Carolina geology and the Cooper River supply source. The Bushy Park Reservoir collects water from the Cooper River, which drains the South Carolina Upper Coastal Plain — the Santee Basin's mix of Cretaceous Black Creek Formation (sandy, low-carbonate coastal plain), Eocene Williamsburg Formation (limestone — some carbonate input), and the Oligocene Cooper Formation (calcareous marl — moderate carbonate). The lower coastal plain setting dilutes dissolved minerals and the Cooper River's relatively modest watershed carbonate contribution produces the moderately soft finished supply at Mount Pleasant. Local groundwater from the Floridan Aquifer equivalent in South Carolina may contribute moderate calcium through blending.

With hardness at 96 mg/L, Mount Pleasant residents experience light to moderate scale accumulation. Faucet aerators and showerheads develop deposits slowly — bi-monthly cleaning with citric acid solution is sufficient. Dishwashers produce clean glassware. Mount Pleasant Waterworks consistently delivers water meeting all South Carolina DHEC and EPA Safe Drinking Water Act requirements.